So then in order to figure out the complete number of valence electrons in our molecule, we just add 5 plus 4 plus 1.

那么接下来为了得到,这个分子中价电子的总个数，我们只需要将五加上四，再加上一。

麻省理工公开课 - 化学原理课程节选

If we look at our last structure here where we have nitrogen the middle, we can also figure out all those formal charges, and in this case we have plus 1 on the nitrogen, we have minus 2 on the carbon, and then we end up with a 0 on the sulfur there.

如果我们来看看最后一个结构,在中间的原子是氮，我们同样可以计算出所有的形式电荷，而在这种情况下，氮为正一，碳为负二，而最后硫为零。

麻省理工公开课 - 化学原理课程节选

It's always a good first approximation, because you need to start somewhere in terms of drawing Lewis structures, but then if you go and figure out the formal charge and you just have lots of charge separation or very high charges, like a plus 2 and a minus 2 and a minus 1 all different places in the atom, what it should tell you is maybe there's a better structure.

它总是一个好的第一近似，因为在画路易斯结构的时候,你总需要一个起点，但是如果你在算出形式电荷之后,发现有很多电荷分开了,或者说有很高的电荷，比如有一个正二，一个负二，还有一个负一1,在原子的各个地方，这应该就是在告诉你,或许还有一个更好的路易斯结构。

麻省理工公开课 - 化学原理课程节选